Ceramicware Defects Handbook/Colour variation

Colour variation

Defects Description

Colour variation between differing batches

The tonal of the underglaze decorations shown has shown significant differences where the colour reproductions are differs from batch to batch

Causes & Solutions

• Glazes

Solutions: Original colour batch are fired alongside with new colour batch to see if there are differences between these two batches. Repeat the test in glazed ware, if there are differences noted, the problem are highly possible resides with glazes used. For examples, low solubility glazes may give brighter colour response but take note that low solubility glazes differ from each other. Potclays 2204 glaze may give superior colour response compared to Potclays 2205 glaze.

• Underglazes coating are too thinly applied

Solutions: If too thinly applied the colour may changed for example from brown to gray

• Differences in firing temperatures

Solutions: Pigment colours that contain selenium, cadmium, copper will burn away at elevated temperatures.

• Sulphur trioxide chemicals may affect colours (browning of chroma green)